CO2 instability.

[Mitelog]

Hi all,

With my plants being in incresingly poorer conditions, i have decided to Check everything a new times !

When i have checked my CO2 , one thing i have noticed is that my regulator is not exactly the same pressure from day to day, one day is at 1,5 bars the second day is at 1,6 or 1,7 bars.

So the bps is never the same from day to day, it vary from 110 to 130 bubbles per minutes , so my ph vary from 6,34 to 6,47 ( degassed water is 7,61)

My regulator is a Tunze 7077/3 , dual stage with needle valve but it is old maybe 10+ years .

Do you think a change like that can be enough to stress my plants ?

Thank’s

 

[Koan]

That amount of variation in pH should not indicate a CO2 fluctuation significant enough to affect the plants

How is the circulation in your tank? Sufficient movement to ensure your CO2 is reaching all the areas of planting around all the hardscape etc is one thing to check

A CO2 test is the best way to identify for certain what your levels are day-to-day. Here is the test we use here in the states:

Carbon Dioxide Chemical Test Kit

The HI3818 is a chemical test kit for the determination of carbon dioxide by manual titration using a phenolphthalein indicator.

www.hannainst.com

Here is a discussion of using it

Resource Thread 'Hanna CO2 Test Kit: My experience so far (and why you're probably not starting CO2 injection early enough)!'

Mar 27, 2025

The 2hrAquarist legend Dennis Wong tested the Hanna Test Kit vs a $3,000+ CO2 testing device and found accurate results in low kH aquasoil based tanks when compared. $30 for CO2 readings vs $3,000+!

It's a simple kit that comes with simple instructions, two differently sized vials for different detection ranges, a titration syringe phenolphthalein indicator, and an NaOH solution of some unknown concentration to titrate with.

For the range of detection on the Hanna CO2 test kit we want (0-50ppm):

• Add 10mL of aquarium water to the small flask. Add 1...

• Naturescapes_Rocco
• co2 co2 measurement hanna injection test kit titration
• Replies: 40
• Forum: Fertilizing and Aquarium Chemistry

• 
• 

I haven't been able to locate this test on the site for Hanna France, you might reach out to them directly to see if it is available

 

[Mitelog]

Hi Koan,
Thank’s for the reply !

The circulation is good all around the tank, my filter is a oase filtosmart 200 ( rated at around 800 liters per hours) and my tank is 90 liters real.

I used my drop checker all around the tank and it’s the same color everywhere


The Green drop checker is with a KH 8 solution (NaHCO3) and the Green /yellow one is a KH 4 .

The 2 vial next to the first drop checker contain buffer solution of 6,8 for the greener and 7 for the bluer. ( i made them at work with phosphate salt and verified with lab quality ph meter, i’m a chemist)

 

[Mitelog]

For the Hanna CO2 test kit, i can’t found it here on Amazon or other website, i will ask my shop owner that sell Hanna product if he can have it

 

[Koan]

For the Hanna CO2 test kit, i can’t found it here on Amazon

i made them at work with phosphate salt and verified with lab quality ph meter, i’m a chemist

CO2 testing is just titration to a phenolphthalein Indicator endpoint with NaOH

All the Hanna test kit does is set you up with specific quantities to take out the molarity calculations portion




You should be able to set yourself up to perform at home pretty easily as well

 

[Mitelog]

Thank’s Koan

I have not the molar concentration of the NaOH solution that Hanna use, so i will not have the same results.

I have found a test kit that use the same process : phenophtaline and sodium hydroxyde, it’s a brand called JBL :

 

[Aquajack]

How have you found that test kit. I have recently purchased the same. Hanna kits here in Aus, the cheapest I could find delivered was $80!.
So I figured I would try this one out. Seems to test quite high though, even when the CO2 isn't running which makes me think how accurate it is.

 

[Mitelog]

I don’t know Aquajack !

I haven’t tried it, i have just found it after the post about the hanna test, and after reading some stuff about it, found it work on the same principle as the Hanna one .

So really don’t know if it’s relliable or not ?

From the comment that i have read about it, it seems correct

 

[Mitelog]

Hi,

So i finally tested my CO2 with the jbl test and it’s in the range i was thinking : the test change color at 35ppm ! ( i tested several times, at different time of the day )

So with all this i made a Yugang like reactor to have more stability on my CO2:
It’s now very stable from day to day !
My degassed water ph is at 7,51 and after 3 hours of the CO2 on, my ph is at a steady 6,32 to 6,34 all the photoperiod.


Now i can rule out the CO2 for my plant problem, but i’m litterally lost as to what can be the cause ???

I have checked my floating plant ( limnobium) and it seem that it is nutrient related :
There are necrosis like this on the older leaves and some deformation on the newer leaves that are also lighter green

I dose everyday 1,8ppm no3 and 0,6ppm po4 via kno3 and kh2po4 and 0,03ppm of fe via a Burr like blend of micro

 

[Naturescapes_Rocco]

Can we see a photo of your tank? How strong is your lighting?

1.8ppm NO3 per day could be somewhat low in a densely planted, high-energy tank. Do you do any extra front-loading of ferts after water change?

 

[Mitelog]

Hi Rocco!

Thank’s for helping me !

So this is the tank 2 months after the start, the 9th décembre, all was growing well, maybe except pogostemon deccanensis (the HC cuba was trimmed so a little yellow on this pic)

This is the tank now :


Full of algae !!! Blue Green, black brush on the rock (spot dosed with h2o2 ), Green hair in the HC (and others plants)

I really don’t understand the problem as in the past, with simple quartz substrate, i haven’t had any problem!

This time, with aquasoil, i can’t figure it out why my plant stunt !


I dose 1,8ppm No3 per day as i estimate my no3 consumption at around 1,5ppm per day ( i tested all day of the week at the same hour, with and with out dosing)
I use the Hanna nitrate checker HR (and also the Phosphate checker)

My current No3 level is 11,83 ppm and po4 is at 0,97 ppm ( if i dont put 0,6ppmPo4 everyday, the level in the tank fall close to 0 ppm in just 48h , due to the aquasoil)

I change 50% per week, RO remineralized to 30ppm Ca and 8 ppm Mg and 5ppm K

I don’t front load any macro or micro , i dose every day, and dose after the water change on the water change day.

My light is led strip: 2 strip in 6500•k white led and 1 band of blue red horticulture led (460nm for the blue and 665nm for the red diod)

Around 15 to 20w total: i mesured the PAR with the photone App at surface just 5 cm below the light : 146 PAR

The par near substrate is around 50

 

[Mitelog]

Some close up view of the plants /algae:




Substrate as been lightly siphoned so not full of mulm etc… filter cleaned regularly and Nh4 are 0ppm (salifert test kit).

 

[Naturescapes_Rocco]

Ok, lots of good things goin on now! All that healthy, new growth is algae-free, so whatever you fixed/changed is clearly working.

The problem is the old algae, stuck and intertwined in the plants. It's going to be a serious issue for you if it's not fixed or removed, in my experience. When the algae mass is as much as you have, I really recommend doing a fairly full reset.

Trim the clean, algae-free tops and set them aside. Gently remove all the lower stems, algae, etc. Do a massive 90% water change, siphon the substrate, and try to remove as much organic debris, algae, rotting stems, leaves, etc as you can. If you can get your substrate back to a clean place, then you should replant those algae-free tops into the newly cleaned substrate, and essentially start all over.

---

I know this seems like a lot of work, and it is, unfortunately -- but it's far less of a headache than what you might deal with! Your new growth is good, but all of that algae will either continue to grow and spread, or if it slowly dies off, the dying algae will continue to release TONS of organics and particles into your water, which will only cause more algae.

In my experience, when the algae is as bad as what you have, you can either 1) Take minimal action, maybe get some good new growth, but forever fight against the cycle of algae, decaying plants, decaying algae, more algae, etc for months and months on end, OR 2) Put in a ton of work to save all of that beautiful new growth you have, remove all of that algae biomass, and get things set on a good course.

That's just my opinion, and I guarantee someone might disagree with me! But I can't tell you how many times I've had the kind of scenario you're in. The best course of action for me always turned out to require hours of effort and patience to reset the tank, but I was able to benefit greatly over the next few months, rather than keep getting frustrated by months of algae only getting slightly better.

 

[Mitelog]

Thank’s for all those advice Rocco ! Really appreciate !

Like i said, i have siphoned the substrate 90% by 2 time and replanted the healthy top, and bin the lower section.

You can see healthy top but there is barely any grow since 2 weeks, it seem that when i arrive at my 3rd or 4th day of dosing micro, the plant seems to stunt ???

The hemianthus was carpeting like crazy in december and now since january it stunt and stunt ? ( and it’s definitly not CO2), i selected the healthy stuff and replanted it but it ended the same.

Is it possible that the aquasoil have a counter productive effect on my plants ? As i’m sure my dosing will work in a inert substrate, regarding my results in the past with inert quartz

 

[CincyScaper]

Have you checked your ammonia level?

 

[Mitelog]

Yes, tested with salifert test kit : 0 ppm